The present application relates to a zoom lens which includes a lens having a focal length which is varied by deformation of the lens material without movement of the lens and effects zooming by the variation of the focal length and a camera module and an electronic apparatus which use the zoom lens.
Reduction in size and weight is demanded for camera modules which use a solid-state image pickup element such as a CCD (Charge Coupled Device) element or a CMOS (Complementary Metal-Oxide Semiconductor) element and also for various electronic apparatus such as image pickup apparatus which use such a camera module. To this end, various methods have been proposed wherein a variable focal length lens having no moving mechanism is used as a zoom lens for use with a camera module. For example, Japanese Patent Laid-Open No. 2008-185627 (hereinafter referred to as Patent Document 1) discloses a technique which uses a variable focal length lens having a deformable lens refracting surface as a converter lens.
The lens of the refracting surface deformation type disclosed in Patent Document 1 is configured such that an elastic film made of a resin material or the like and having optical transparency is adhered to an optically transparent substrate formed as a flat plate or having a predetermined curved surface by a sealing material, and optically transparent liquid or the like is filled in the inside. By varying the pressure applied to the material filled between the transparent substrate and the elastic film to deform the resilient film, the curved surface shape can be varied to vary the focal length of the lens. As a lens whose curved surface shape is varied in this manner, a liquid lens having liquid filled therein, a gel lens having gel filled therein and so forth have been proposed.
A schematic sectional configuration of an example of a variable lens of such a refracting surface deformation type as described above is shown in FIG. 69. Referring to FIG. 69, the variable lens 82 shown includes an optically transparent substrate 81 provided on one surface thereof and made of a material such as glass or resin, and a deformation film 87 provided on the other surface thereof and formed from an optically transparent elastic film or the like. A joining member 84 of a joining material or the like is interposed between a pair of, for example, ring-shaped framework members 83 and 85 such that the outer circumference of the optically transparent substrate 81 and the deformation film 87 is held liquid-tight by the joining member 84. An optically transparent medium 90 having fluidity such as liquid or gel is sealed in a region defined by the members mentioned to form the variable lens 82 of the refracting surface deformation type. A liquid moving member 86 in the form of a pipe or the like is provided on the variable lens 82, in the example shown, at a portion of the joining member 84, such that the medium 90 can be introduced into and extracted from the inside of the variable lens 82 therethrough. An external pump mechanism or the like not shown is driven to vary the volume of the medium 90 in the variable lens 82. By the variation of the volume of the medium 90, the deformation film 87 can be deformed to change the focal length of the variable lens 82 within a range from a convex lens to a concave lens. It is to be noted that the deformation mechanism may not only be such a mechanism for feeding and taking the medium 90 into and out from the inside of the variable lens 82 but be a mechanism which varies the pressure to the deformation film 87 by deformation of the framework member 83 or 85 or the like. Thus, the mechanism for varying the pressure to the deformation film 87 is not limited particularly.
As the medium in the variable lens 82, it is preferable to use a material having optical transparency and having a suitable refractive index such as silicone type oil. Meanwhile, as a material of the deformation film 87, it is preferable to use a deformable material having suitable elasticity and having required optical transparency such as silicone type rubber, and the deformation film 87 preferably has a shape of a deformable thin film or the like.
By adopting such a configuration as described above, the lens power can be made variable simply by a comparatively simple and easy mechanism such as a mechanism for varying the pressure to the deformation film 87 of the medium 90, for example, a mechanism for sucking or injecting the medium 90 or the like. By utilizing such a variable lens 82 as just described, variation of the focal magnification can be implemented, and, for example, by combining a plurality of such variable lenses 82 as shown in FIG. 2, such a wide converter as disclosed in Patent Document 1 can be implemented by a simpler configuration.
Also it is investigated to utilize a variable focal length lens of the electro-wetting type which utilizes an electro-wetting phenomenon and wherein two different kinds of liquid including polar liquid and non-polar liquid are accommodated in a vessel and a voltage is applied to deform the shape of the interface between the two kinds of liquids thereby to vary the focal length. A zoom lens which uses the variable focal length lens of the electro-wetting type just described is proposed, for example, in Japanese Patent Laid-Open No. 2008-089752 (hereinafter referred to as Patent Document 2).